This application claims priority under 35 U.S.C. .sctn. .sctn. 119 and/or 365 to Hei 9-349844 filed in Japan on Dec. 12, 1997, the entire contents of which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a device for and a method for obtaining a motion vector by dividing a moving picture or image into a plurality of blocks and detecting motion vectors in each block.
2. Description of the Prior Art
Motion vector detection technique which are typically used to encode video information commonly use a block matching method has been commonly used which divides a present picture or image into a plurality of blocks and performs pattern matching with reference images in each block.
FIG. 21 is a block diagram illustrating an exemplary configuration of a conventional motion vector detecting device which uses such a block matching method. In FIG. 21, reference numeral 21 indicates a motion vector detector circuit for detecting each motion vector. Reference numeral 22 indicates a predicted image signal corresponding to an image signal indicative of the present picture or blocked image, which is input to the motion vector detector circuit 21. Reference numeral 23 indicates a control circuit for controlling the entire operation of the motion vector detecting device. Reference numeral 24 indicates an address signal outputted from the control circuit 23. Reference numeral 25 indicates a frame memory for storing an image signal. Reference numeral 26 indicates an image signal such as a local decoded image or the like. Reference numeral 27 indicates a reference image signal read from the frame memory 25. Reference numeral 28 indicates a signal outputted from the motion vector detector circuit 21, which includes an optimum motion vector and an optimum evaluated value, such as the sum of absolute differential values of pixels between a predicted image and a reference image related to the optimum motion vector or the like.
The operation of the motion vector detecting device will next be explained.
The motion vector detector circuit 21 compares a predicted image signal with a reference image signal 27 read from the frame memory 25 to determine an optimum motion vector and an optimum evaluated value, which are subsequently output as an output signal 28.
The motion vector detector circuit 21 also determines motion vectors according to block matching for luminance and color-difference signals. Thus, as shown in FIG. 22, if the block size of a luminance signal Y and color-difference signals Cb and Cr related to an image to be subjected to a block matching process are identical (for example, the horizontal and vertical directions include 16 pixels respectively as shown FIG. 22), then a circuit for determining an optimum luminance vector from the luminance signal Y can be employed to obtain an optimum color-difference vector from the color-difference signals Cb and Cr.
Image encoding systems such as an MPEG (Moving Picture Experts Group) 2 commonly use, formats such as a "4:2:2 format," in which the horizontal sizes of blocks for the color-difference signals Cb and Cr are respectively equal to 1/2 the block size of a luminance signal Y (as shown in FIG. 23), or a format such as "4:2:0 format", in which the horizontal and vertical sizes of blocks for color-difference signals Cb and Cr are respectively 1/2 the block size for a luminance signal Y (as shown in FIG. 24)
Thus, when blocks for a luminance signal Y and color-difference signals Cb and Cr have different sizes, significantly different circuit configuration are usually relied on to obtain an optimum luminance vector and an optimum color-difference vector.
Since the conventional motion vector detecting device and method are configured in the above-described manner, the circuit configuration of the optimum luminance vector determining circuit and the optimum color-difference vector determining circuit are different, thereby increasing development costs and lowering general versatility.